We propose to study the characteristics of a variety of established human lymphoblastoid cell lines in an effort to: a) distinguish those characteristics which are essential for continual proliferation from the special characteristics of cell lines due to their lineage; b) elucidate the mechanism of Epstein-Barr virus induction in cells and determine the mechanisms responsible for the maintenance of the latent virus state and for its breakdown. We expect to accomplish these goals by the following lines of work: 1) Determination of specific virus products which can be quantitatively assayed as a measure of virus function. We have evidence for a special thymidine kinase present in lymphoblasts which may fit this requirement. 2) Studies of the effect of halogenated pyrimidine deoxynucleosides to determine the role of bromodeoxyuridine and iododeoxyuridine in virus induction. 3) Comparison of membrane components in lymphoblast lines and in lymphocytes, including lymphocytes stimulated by plant lectins in an attempt to separate those components associated with proliferation from those reflecting the specificity of particular lymphocytes. The overall goals of this work are: 1) An understanding of the control of proliferative capacity in lymphoid cells; and 11) Elucidation of the mechanisms controlling the production of "temperate" virus products in animal cells.